# Impact of sampling depth on CO2 flux estimates

## TL;DR

This study shows that CO2 flux estimates between the ocean and atmosphere vary significantly based on sampling depth and wind conditions.

## Contribution

The study quantifies how CO2 flux estimates change with sampling depth and highlights the importance of considering these factors for accurate carbon budget assessments.

## Key findings

- CO2 flux estimates at 1 m depth are 97.6% higher than at 5 m depth in the Atlantic basin.
- Sampling depth impacts CO2 flux estimates by up to 71% in sheltered regions and 44% in exposed regions.
- Higher wind speeds correlate with larger CO2 fluxes, while sunny hours increase pCO2 levels.

## Abstract

The exchange of trace gases between the atmosphere and the ocean plays a key role in the Earth’s climate. Fluxes at the air-sea interface are affected mainly by wind blowing over the ocean and seawater temperature and salinity changes. This study aimed to quantify the use of CO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2 partial pressure (pCO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2) measurements at different depths (1, 5, and 10 m) in ocean surface layers to determine CO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2 fluxes (FCO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2) and to investigate the impacts of wind-sheltered and wind-exposed regions on the carbon budget. Vertical profiles of temperature, salinity, and pCO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2 were considered during a daily cycle. pCO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2 profiles exhibited relatively high values during sunny hours, associated with relatively high sea temperatures. However, the largest FCO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2 corresponded with higher wind speeds. Estimated fluxes between measurements at 1 and 10 m depths decreased by 71% in the sheltered region and 44% in the exposed region. According to the SOCAT dataset, at a depth of 5 m, the Atlantic basin emits approximately 0.29 Tg month\documentclass[12pt]{minimal}
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\begin{document}$$^{-1}$$\end{document}-1 of CO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2 to the atmosphere; nevertheless, our estimates suggest that FCO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2 at the surface is 12.02 Tg month\documentclass[12pt]{minimal}
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\begin{document}$$^{-1}$$\end{document}-1, which is 97.6% greater than that at 5 m depth. Therefore, future studies should consider sampling depth to adequately estimate the FCO\documentclass[12pt]{minimal}
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\begin{document}$$_{2}$$\end{document}2.